Electrostatic reproducer



March 10, 1931. R, LE 1,796,155

ELECTROSTATI C REPRODUCER Filed July 29, 1929 2 Sheets-Sheet l @WWM March 10, 1931. R R 1,796,155

ELECTROSTAIIC REPRODUCER Filed July 29, 1929 2 Sheets-Sheet 2 Patented Mar. 10, 1931 UNITED STATES PATENT OFFICE RALPH H. LEFFLER, OF DEERFIELD, ILLINOIS, ASSIGNOR TO CARTER RADIO COMPANY, OF CHICAGO, ILLINOIS, A CORPORATION OF ILLINOIS ELECTROSTATIC REPRODUCER Application filed July 29,

My invention relates to reproducers, and more particularly, in the form illustrated herein. to electrostatic reproducers.

In the form of the invention illustrated herein, the invention is applied to a reproducer or pick-up mechanism of the condenser type. The pick-up device is of such a nature that it may operate in a multiple manner in such a way that as it produces a certain effect in one instrumentality it may produce an equal and opposite effect in another instrulnentality, so that these two effects, if desired, may be used cumulatively to produce a final result, which may thus be much larger than would be produced by one of the original effects alone. The manner in which this cumulative effect may be brought about is more thoroughly explained in connection with my co-pending application Serial No.

309,551, filed October 1, 1928. v

In this application I am not describing the rcproducer in connection with any circuits or allied instrun'lentalities, but am confining the description purely and simply to the reproducer itself.

My invention has for one of its objects the provision of a reproducer which is so constituted that it will compensate for the varying amplitudes of sounds of different frequency as impressed upon a record by the constant velocity process of cutting. Records for use with magnetic pick-ups, the type of pick-up c 'minonly used, have the sound grooves cut therein bv a stylus moving at a constant velocity. The reason for this lies in the fact that the voltage obtainedfrom a magnetic pick-up depends upon the number of lines of force out per unit of time. Now, if the velocity of the cutter changed with the frequency, the rate of cutting lines of force would also change so that high frequencies would generate a much higher voltage than low frequencies of the same sound volume.

The result of this method of cutting upon i the sound groove of the record is to make the low frequency curve of greater amplitude than the high frequency curve. Also an ad vantage is obtained by this method of cutting because if the amplitude of the curves of the 0 sound groove in the record decreases as the 1929. Serial N0. 381,800.

frequency increases, then the peaks of the curves are less sharp than they would otherwise be.

Now, however, with my type of pick-up slnce it is the amount of lateral displacement of the stylus which effects the change in voltage, the tendency is to over emphasize the low frequencies because of their greater amplitude in the sound groove, so I provide means for compensating for this error. In order to bring this about,.m'y invention, when used in its preferred form, operates along three separate and distinct lines.

It is a further object of my invention to reduce the side pressure or force which opposes the stylus when traveling in a groove, and especially to reduce friction on side walls of record curves having large amplitudes where the stylus displacement is the greatest. Also to reduce the Wear on curves having small radii of curvature, thus to increase the life of records and conserve the apparatus in general.

It is a further object of my invention to have my improved reproducer so constructed that, while it reduces the equivalent sound intensity of the larger amplitude low frequencies to bring them into harmony with high frequencies, it still maintains the normal intensity of the higher high frequencies.

It will, of course, be understood that my invention is not to be construed as necessarily requiring all of the refinements as herein described in order to come within the scope of the appended claims. I am describing herein, however, one form of the invention having certain refinements which I have found will produce the results above outlined. I will describe this form of the invention more in detail by referring to the accompanying drawing, in which,--

Fig. 1 is a longitudinal sectional view on line 1 of Fig. 2;

Fig. 2 is a sectional view on line 2-2 of Fig. 1; i

Fig. 3 is a bottom view of the device, certain parts being broken away more clearly to reveal features of construction;

Fig. 4 is a fragmentary sectional View on line 4--4= of Fig. 1;

between them a condenser plate 12 which is adapted to be flexed due to theactuations of a stylus 13. The plate 12 is securely held in position between the horizontal legs of the plates 10 and 11, there being interposed suitable damping elements 14 and 15, which serve a purpose presently to be explained.

These damping elements 14 and 15 may desirably be made of metal-plated bakelite. The condenser plate 12 has a stylus carrier 15 riveted to its lower end, which stylus carrier serves at the same time as one of the elements of the pivotal mounting for the lower extremity of this plate 12. The remaining elements of this pivotal mounting are two flexible arms 16 and 17 securely fas-v tened to the vertical legs of the base plates 10 and 11 by means of screws 18 and 19. These flexible arms preferably have knifeedge extremities at their interior ends, and these engage the stylus carrier 15 so that a pivotal action may take place as the stylus 13 moves in the groove of a phonographic record, for instance. The flexible condenser plate 12 is associated with two fixed plates 20 and 21, which fixed plates are riveted to insulating carriers 22,23, as, for instance, by the rivets 24. V

In order to control the size of the air gap between the plate 12 and the plates 20 and 21, I provide an adjustable mounting for the carriers 22 and 23. To bring this about, these carriers are pushed inwardly by means of heavy springs 25 and 26, respectively, that are moved outwardly against the action of these springs by adjustment screws 27 and 28, and also additional adjustment screws 29 and 30. It will be noted that each carrier is drawn outwardly against the action of the s ring by three adjustment screws, so that t e condenser plates 20 and 21 are susceptible of what is practically a universal adjustment in so far as the purposes of this invention are concerned. The base plates 10 and 11 are held together by four screws 31, 32, 33 and 34. The screws 27, 28, 29 and 30 preferably engage metallic bushings 35 provided in the insulating carriers 22, 23. Suitable connections 36 and 37 are electrically secured to the fixed condenser plates 20 and 21,- as by rivets 38.

The stylus' 13 is removable, and is held in place by the set screw 40.

Now, if the particular device as herein used' for illustrative purposes is hsed, for instance, in connection with a phonograph record the groove of which has been constructed upon the constant velocity principle, then the operation and its compensating effect will be in general as follows:

Such grooves are shown, for instance, at 39 and 39 in Fig. 8. Groove 39 shows, for instance, a groove of large amplitude and low frequency, while 39 represents a groove of high frequency and therefore of less amplitude. I

Assuming that the stylus 13' moves to the right, it tends to bow the plate 12 to the left, as shown in Figs. 5 and (5, thus increasing the capacitative effect between elements 12 and 20 and decreasing it between the elements 12 and 21. The degree of capacitance change is not a linear function of the degree of movement of the stylus. The degree of capacitance change is less and less proportionately as the stylus moves away from its central position because of the bowing of the plate. If the constants of the device are properly chosen, this decreasing rate of response furnishes a large measure of compensation for the difference in amplitude in the record grooves representing the high and the low frequencies. A further compensating influence is brought about by reason of the pivotal or preferably knife-edge engagement between the elements 15 and the arms 16 and 17. As the stylus moves to the right, for instance, to. thus bow the plate 12 to the left, the arm 17 is carried upwardly, and as its extremity moves along the arc of a circle it necessarily, though slightly. bodily carries the stylus carrier 15 to the right, thus again decreasing the result produced pro rata by the movement of the plate 12. Similarly, the fact that the inner extremity of the plate 17 moves upwardly tends to bring about an additional compensating effect because the point about which the pivotal action is taking place is brought closer to the fixed end of the plate 12,.thus increasing the degree of curvature of this plate.

I have found that by a proper design of the elements employed, more particularly what I might call the knife-edge or similar pivotal mounting, I can compensate in a measure to faithfully reproduce the sounds in the manner in which they were originally emitted when impressed upon the record. In records out upon the constant velocity principle, the higher the frequency the lower the amplitude.

In addition to toning down the large amplitude effects of the lower frequencies, it is of great value to assist the reproduction by maintaining the normal intensities of the higher frequencies. This is brought about by the damping elements 14 and 15. These damping elements 14 and 15 are so chosen that they have a certain degree of resilience, 1

be clear to those skilled in the art.

or what might be called compressibility. They can be more easily compressed during the initial movement of the plate 12, but will resist increasingly further tendency toward compression. The plate 12 is thus more free to move at the inception of its movement, by reason of these damping elements, than it is later on. It will thus be seen that the plate 12 has greater liberty of response for the higher frequencies. All of these various compensating efl'ects make it possible for me to reproduce faithfully the original sounds.

In Fig. 7 I show a result that I am able to obtain by the use of my invention in that the pressures exerted against the stylus by the plate 12 as it is being bowed are measured vertically and the stylus displacement is measured horizontally. As the stylus moves, the curve 41 would normally represent the increasing pressure, which would be a result of the increased dis lacement of the stylus. By reason of the yiel ing nature of the mountin g, including the elements 16 and 17, and the co-operative effect of the movement of the various parts, this pressure is materially reduced so that it more nearly approximates a straight line 42. In this manner I am able to conserve the records and have other corre sponding benefits.

From what has been thus described, it is thought that the nature of my invention will It is, of course, apparent that my invention is equally applicable to a single-acting device, instead of a double-acting one, as here shown. Having, however, thus described one form which my invention may take, what I- claim as new and desire to secure by Letters Patent is:

1. A device of the character described comprising two relatively adjustable elements,-

one of said elements being flexible, adapted to be bowed and carrying means adapted to interact electrically with said other element, means for mounting one extremity of said flexible element, a swingable support for said flexible element near its other extremity whereby said flexible element at said last e'xtremity is capable of a substantially pivotal movement, and means for actuating said flexible element to bring about more or less bowing in a selected manner.

2. A device of the character described comprising two relatively adjustable elements,

one of said elements being flexible, adapted to be bowed and carrying means adapted to interact electrically with said other element, means for mounting one extremity of said flexible element, a swingable support for said flexible element near its other extremity whereby said flexible element at said last extremity is capable of a substantially pivotal movement, and a stylus for actuating said flexible element to bring about more or less bowing in a selected manner.

3. A device of the character described comprising two relatively adjustable elements, one of said elements eing flexible, adapted to be bowed and carrying means adapted to interact electrically with said other element,

means for mounting one extremity of said flexible element adapted to increasingly oppose the movement of said element with an increase of the bowing movement, a swingable support for said flexible element near its other extremity whereby said flexible element at said last extremity is capable of a substantially pivotal movement, and means for actuating said flexible element to bring about more or less bowing in a selected manner.

4. A device of the character described comprising two relatively adjustable elements. one of said elements being flexible, adapted to be bowed and carrying means adapted to interact electrically with said other'element, means for mounting one extremity ofsaid flexible element adapted to increasingly oppose the movement of said element with an increase of the bowing movement, a swingable support for said flexible element near its other extremity whereby said flexible element at said last extremity is capable of a substantially pivotal movement, and a stylus for actuating said flexible element to bring about more or less bowing in a selected manner.

5. A device of the character described comprising two relatively adjustable elements. one of said elements being flexible, adapted to be bowed and carrying means adapted to interact electrically with. said other element, means for mounting one extremity of said flexible element, a pair of aligned convergmg swingable supports for said flexible element near its other extremity whereby said flexible element at said last extremity is capable of a substantially pivotal movement, and means for actuating said flexible element to bring about more or less bowing in a selected manner.

6. A device of the character described comprising two relatively adjustable elements. one of said elements being flexible, adapted to be bowed and carrying means adapted to interact. electrically with said'other element, means for mounting one extremity of said flexible element, a pair of aligned converging swingable supports for said flexible element near its other extremity whereby said flexible element at said last extremity is capable of a substantially pivotal movement, and a stylus for actuating said flexible element to bring about more or less bowing in a selected manner.

7 A device of the character described comprising two relatively adjustable elements. one of said elements being flexible, adapted'to be bowed and carrying means adapted to interact electrically with said other element,

whereby said flexible element at said last extremlty is capable of a substantially pivotal movement, and means for actuating said flexibleelement to bring about more or less bowing in a selected manner.

8. A device of the character described comprising two relatively adjustable elements, one of said elements being flexible, adapted to be bowed and carrying means adapted to .interact electrically with said other element,

means for mounting one extremity of said flexible element adapted to increasingly oppose the movement of said element with an increase of the bowing movement, a pair of aligned converging swingable supports for said flexible element near its other extremity whereby said flexible element at said last extremity is capable of a substantially pivotal movement, and a stylus for actuating said flexible element to bring about more or less bowing in a selected manner.

9. A device of the character described comprising two relatively adjustable elements, one of said elements being flexible, adapted to be bowed and carrying means adapted to interact electrically with said other element,

means for mounting one extremity of said flexible element, a swingable knife-edge support for said flexible element near its other extremity whereby said flexible element at said last extremity is cable of a substantially pivotal movement, and means for actuating said flexible element to bring about more or less bowing in a selected manner.

10. A device of the character described comprising two relatively adjustable elements, one of said elements being flexible, b

adapted to be bowed and carryin means adapted to interact electrically with sald other element, means for mounting one extremity of said flexible element, a swingable support for said flexible element near its other extremity whereby said flexlble' element at said last extremity is capable of a substantially pivotal movement, and means for actuating said flexible element to bring about more or less bowing in a selected manner,'said flexible element being so proportioned that within the limits of its normal movement the bowing action is a decreasing 'function relative to the applied force.

11. A- device of the character described comprising three elements substantiall parallelly aranged, the middle one of said elements being flexible, adapted to be bowed, and carrying means adapted to complementarily interact electrically with said remaining elements, means for mounting one extremity of said flexible element adapted to increasinglyoppose the movement of said element with an increase of the bowing movement, a'pair of aligned converging swingable supports for said flexibleelement near its other extremity whereby said flexible element at said last extremity is capable of a substantially pivotal movement, and means for actuating said flexible element to bring about more or less bowing in a selected manner.

12. A device of, the. character described comprising three elements substantially parallelly arranged, the middle one of said ele-.

ments being flexible, adapted to be bowed, and carrying means adapted to complementarily interact electrically with said remaining elements, means for mounting one extremity of said flexible element adapted to increasingly oppose the movement of said element with an increase of the bowing movement, a pair of aligned converging swingable supports for said flexible element near its other extremity whereby said flexible element at said last extremity is capable of a substantially pivotal movement, and a stylus for actuating said flexible element to bring about more or less bowing in a selected manner.

13 A device of the character described comprising three elements mounted side by side, the center one of said elements being flexible, adapted to be bowed and carrying means adapted to interact electrically and complementarily with the other two elements, means for mounting one extremity of said flexible element, a swinga-ble support for said flexible element near its other entremity whereby said flexible element at said last extremity is capable of a substantially pivotal movement, and means for actuating said flexible element to bring about more or less bowmg in a selected manner, said flexible element eing so proportioned that within the limits of its normal movement the bow-ing action is 2ft decreasing function relative to the applied orce.

14. A device of the character described comprising two. relatively adjustable elements, one of said elements beingflexible, adapted to be bowed and carrying means adapted to interact electrically with said other element, means for mounting one extremity of said flexible element, a swingable support for said flexible element near its other extremity whereby said flexible element at said last extremity is capable of a substantially pivotal movement, and means for actuating said flexible element to bring about more or lessbowing in a selected manner, said flexible element being so proportioned that within action causes a decreasing function of applied force relative to displacement from the normal posltion.

In witness'whereof, I hereunto subscribe my name this 25th day of July, A. D. 1929.

RALPH H. LEFFLER.

the'limits of its normal movement the bowing 

